The proposed work seeks to understand processing of visual information at the cortical level. Specifically, visual function of striate cortex and the different visual areas which comprise prestriate visual cortex will be compared. The major technique employed is that of single unit recording in awake, trained animals. Animals are trained to maintain fixations to study response properties of cells in the different cortical areas. Areas will be compared with respect to orientation tuning, directional selectivity, contrast senitivity, color opponency, etc. Another way in which striate and prestriate areas may differ is in the role of the afferents from the pulvinar nucleus of the thalamus. As a first step in analyzing the function of the pulvinar input response properties of cells in 17, 18 and 19 will be studied after pulvinar lesions and compared to response properties seen in normal animals.